Ultrahigh-frequency directional coupling apparatus



y 1952 T. MORENO 2,602,859

ULTRAHIGH-FREQUENCY DIRECTIONAL COUPLING APPARATUS Filed March 11, 1947 5 Sheets-Sheet 1 lNVENTOR THEODORE MORE/V0 ATTORNEY July 8, 1952 T. MORENO 2,602,859

' ULTRAHIGH-FREQUENCY DIRECTIONAL COUPLING APPARATUS Filed March 11, 1947 3 Sheets-Sheet 2 $29.44. 7 I? W, IGZ M 2 19. 4 51 INVENTOR 72/5000'RE Mama-N0 ATTORNEY u y 5 T. MORENO 2,602,859

ULTRAHIGH-FREQUENCY DIRECTIONAL COUPLING APPARATUS Filed March 11, 1947 3 Sheets-Sheet 3 INVENTOR. 74:00am: MORE/V0 ATTORNEY transmission line.

Patented July 8, 1952 ULTRAHIGH-FREQUENCY DIRECTIONAL COUILING APPARATUS Theodore Moreno, Cambridge, Mass, assignor to The Sperry Corporation, a corporation of Delaware Application arm 11, 1947, Serial No. 733,913

11 Claims.

The present invention relates to electromagnetic energy couplers between ultra-high-frequency energy transmission lines, .such as wave guides, dielectric guides, coaxial lines, or the like, and in particular relates to directional couplers between two such ultra-high-frequency transmission lines.

In order to connect measuring apparatus to an ultra-high-frequency energy transmission system, some means of radio frequency energy coupling must beprovided. Such coupling means should preferably operate independently of the standing waves which may exist in the transmission line, and the amount of power which is extracted from the transmission lin should preferably be a definite fraction of the power which is to be transmitted along the main transmission line. To obtain these advantageous conditions, it is highly desirable that the coupler operate in such a manner that an electromagnetic wave travelling in a single direction along the main line induces a wave travelling in a single direction along the coupling line.. Likewise, a wave travelling in the opposite direction in the main line should induce a wave travelling in the opposite direction in the coupling line. A coupler which has these properties is known as a directional coupler.

The performance of a directional coupler may be described in terms of two quantities:

l. Attenuation- 1me attenuation of a coupler is the strength of the travelling wave in the main line relative to the strength of the travelling wave which it induces in the auxiliary or'coupling line.

Thisis' a power ratio, usually expressed in decibels.

2. Directim'typ0nly in the ideal coupler doe a single wave travelling in the main line induce the auxiliary line. The induced Waves'are normallygreatly unequal in strength. Their relative .strength is the directivity of the coupler, also expressed in decibels.

One such known directional coupler consists of a short'section of auxiliary rectangular wave guide coupled to a main rectangular wave guide A narrow wall of the auxiliary section is fastened rigidly to a narrow wall of the main guide, keeping the longitudinal axes of both guides parallel. Coupling is provided between the main wave guide and the auxiliary section by a pair of longitudinally spaced holes in the commonnarrow side wall. A travelling wave in the main guide will induce a travelling wave in the auxiliary guide travellingin the same direction, since th path length of waves induced in the auxiliary guide through the first hole is equal to the path length of the waves induced therein through the second hole, and noelectrical interference will occur. However, the-path length of the oppositely directed travelling-waves induced through the two holes into the auxiliary guide will beunequal. If this path length difference is equal to a half-wavelength, cancellation will result and no resultant wave will be induced in the auxiliary guide in a direction opposite to that of the travelling wave in the main guide. Q

In order to achieve such a half-wavelength path difference, it is necessary thatthetwo holes ,be spaced one-quarter of a wavelength apart. This, of course, results in the directivity of the coupler being frequency-sensitive, and high; directivity occurs only at a single operating frequency; Furthermore, since the auxiliary wave guide is, oriented parallel to ,the main guide, it becomes somewhat awkward to make any desired wave guide connections to the auxiliaryguide unless bends or elbows are provided in the ends of the auxiliary section. Also, .since.the; two guide sections are connected side by side. along their narrow wall, the coupler is .bulky anduis somewhat difficult to handle.

An illustrative coupler constructed in accordance with the present invention comprises a short section of auxiliary rectangular wave guide mounted at right angles to a main rectangular wave guide section with. the two guides having their broad faces in contact. Coupling Lis accomplished between the two guides by meansfof a pair of apertures cutinto the common wall sec.- tion. The center lines of the two guides effectively divide the common wall section intojfour quadrants and the pair of apertures are situated in diagonally opposite quadrants. By proper .selection of aperture shape and correct positioning in the common wall section, in accordance with the principles .of the invention, it is possible to construct a directional coupler having directivity properties which are substantially independent of the frequency of the wave energy travelling in the main guide.

The present invention therefore providesa directional coupler which has a high directivity that is essentially independent of frequency, thus greatly .increasing' its utility. The convenient mechanical arrangement of the wave guide sections permits conventional wave guide coupling to either end of the auxiliary guide without the use of elbows, and the arrangement further presents a compact coupler which may be easily handled.

An additional advantage of the present coupler is in the wide design latitude which enables one to select the attenuation value-of the coupler as desired. Since the'attenuation varies with aperture size, shape and disposition, many design parameters are available which permit the coupler attenuation to be selectedfrom a broad range. 7

It is, therefore, an object of the present invention to provide a directional coupler having a high directivity that is essentially independent of.

-It is'still another object of the present invenv tion to provide a coupler formed of a pair of coupled transmission lines in-which theattenuation between the two lines may be selected from a. broad range of values.

The invention also relates to the novel features or principles of the instrumentalities described herein, whether or not such are used for the stated objects, or in the stated fields or combinations.

Other objects and advantages of the present invention will become apparent from a consideration of the following specification and attached drawing, wherein: V

-Fig. 1 shows a perspective view of the arrangement of wave guides in a coupler according to the invention, with a cut-away portion showing the couplingv slots; 7

3 Fig.2 shows the instantaneous pattern of surface current and magnetic field inside a rectangular wave guide excited in the dominant mode;

3 shows diagrammatically the arrangement of coupling slots shown in coupler of Fig.. 1;

Figs..4a, band are time graphs of ma-netic field intensities at various points in the coupler shown in Fig. 1 useful in explaining the, operation thereof; .and

Figs; 5-8 show modifications of the slot arrangement of a coupler constructed according to the invention.

v Fig. 9 showsa perspective view of a modification of the coupler according to the invention in which the coupling slots are replaced by coupling loops, andshows how the guides may be separated a desired distance apart.

Fig. 10 shows another view of the device illustrated in Fig. 9.

Fig. 1 shows one form of coupler according to the invention illustrated in wave guide form. Referring to Fig. 1, there is shown a pair of rectangular wave guides l0 and H having their broad faces in contact and their axes perpendicularto one another. Energy is transferred between wave guides I0 and l l by means of coupling slots [2 and I3 cut in the broad wall section which is common to the two guides. Slots l2 and [3 are disposed parallel to the longitudinal axis of wave guide It) and are positioned equidistantly on opposite sides of the center line H! of the upper face of wave guide [0. They are also displaced equidistantly on opposite sides of intensity) varies as 4 the center line l5 of the lower face of wave guide II.

The instantaneous magnetic field that exists in wave guide I0 when excited in the dominant mode is shown in Fig. 2. The instantaneous surface current pattern is also shown. On the narrow faces of the wave guide,-components of surface' current represented b'y solid lines 20 flow only in the y direction (guide thickness) and the current density is independent of the y dimension. Correspondingly, the tangential magnetic field (represented by lines 2|) at the surface of the narrow faces has components only in the axial or z direction.

On the broad faces of the guide, the surface current has components both in the a: and 2 directions. The 2 component of surface current density (and correspondingly the a: component of magnetic field intensity) varies as SID.

reaching a maximum Value at the center of the broad face and falling to zero at .the edges. The a: component of surface current density (and correspondingly the 2 component of magnetic field CO5- I a reaching a maximum at the edges of the broad face, and passing through zero with a reversal of phase at the center. This reversal of phase is important to note, as it leads to the marked frequency-independent directivity that is characteristic of a wave guide directional'coupler constructed according to the teachings of this invention.

Fig. 3' shows diagrammatically the arrangement of coupling slots l2 and I3 of the directional coupler shown in Fig. 1. These" slots are used -'to couple the axialmagnetic field (the z component of magnetic field) in wave guide IQ to the transverse magnetic field (the :r component of magnetic field) in wave guide II. If a signal is fed in from the left end of guide l0, slot l3 receives maximum excitation first, and slot l2 receives maximum excitation a short time later, because of its longitudinal axial displacement d1 relative to slot I3. Electrically slot [3 receives maximum excitation at a phase different from slot 12 by an amount B1d1+1r where B1 is the phase constant of the guide [0 and equals 2r divided'by the wavelength of the transmitted energy as measured in the -'wave guide. The phase difference Bldl arises from the longitudinal displacement d1 of the two slots and the quantity 1r arises from the phase difference between the axial magnetic fields on the opposite sides of the center line 14 of guide I0.

The curves shown in Figs. 4a, 4b and 40 may aid in understanding the phase relationship of the various waves induced in the auxiliary guide It through the coupling. holes I2 and I3. Fig. 4a is a time plot'of the magnetic field intensity induced in auxiliary guide H by each slot, measured at the location 'of the inducing slot'itself. That is, curve H13 is a time plot measured at slot I3 of the magnetic field intensity induced in guide H by slot [3. Curve H1: is a time plot measured at slot l2 of the magnetic field intensity induced in guidel l by slot l2. It will be noted that curve H12 lags behind'Hia by phase delay of amount B1d1+1rJ As stated above, the phase difference Bidi is due to the longitudinal displacement d1 of the two coupling slots along guide I0 and the quantity 1r is due to the opposite phases of the magnetic field at opposite sides of the center line vMoi wave guide Ill.

The wave H13 induced in guide II by slot I3 will travel along guide II in both directions, as will the wave H12 induced therein by slot I2. The wave induced by slot I3 which travels toward; slot 12 will be delayed in guide II with respect to the wave induced by slot I2 travelling in the same direction by an amount equal to Bzdz, where B2 is the phase constant of wave guide II and d2 is the separation between slot I3 and slot I2 measured along guide II.

Figure 4b is atime plot of the magnetic field intensity measured at the location of slot I2,

using the same time scale as in Fig. 4a. Curve Hm is a time plot of the magnetic field intensity of the wave induced 'byslot I3 and travelling toward slot I2 as measured at. slot I2 and curve H1zis-a measure of the magnetic field intensity of the wave H12 induced by slot I2 also measured at slot I2. .It can be seen that curve H13 has been shifted in phase from its position in Fig. 4a. by an amount Bzdz. This is because in Fig. 4b the magnetic field intensities are all taken at slot I2, and a wave travelling in guide II the distance d2 from slot I3 to slot I2 would suffer a phasedelay equal to Bzdz. It is readily seen from Fig. 4b that curves H13 and H12 are approximately 1'80 out of phase and as such will tend to cancel each other. If phase displacement B1d1 exactly equals phase displacement Bzdz the two waves will be exactly out of phase and complete cancellation will result if their amplitudes are equal.

Fig. 4c is a time plot of the magnetic field intensities measured at the location of slot I3 and shows how the induced waves travelling in guide II in .a direction from slot I2 toward slot I3 combine. Curve Hnis, as in Fig. 4a, a time plot measured at slot I3 of the magnetic field intensity of the wave induced by slot I3. Curve H12 is a time plot also measured at slot I3 of the magnetic field intensity of the wave induced in guide II by slot I2. In this figure it is seen that the wave of curve H12 sufiers an additional phaselag from its position in Fig. 4a (measured at slot I2) of Bzdz. This additional phaselag causes, in general, the wave represented by curve H13 to reenforce the wave represented by curve H12 with the result that a resultant wave will travel'in guide I I in a direction from slot I2 to slot I3."

The complete cancellation of the induced waves in guides II which travel in the direction from slot I3 toward slot I2 occurs when phase displacement B1d1 exactly equals phase displacement Bzdz as shown in Fig. 4b. The magnitude of the phase constant B is dependent only upon the guides cross-sectional dimensions and the frequency of the energy being transmitted through the guide. Therefore, if the coupler is constructed of two guide sections having the same cross-sectional dimensions, as is the usual case, the phase constants of the two guide sections will be equal regardless of the frequency of the energy being transmitted Of course, the magnitude of .B will change with changing frequency, but the two phase constants will remain equal.

Therefore, by making the dimensions .111 and dz equal in a coupler formed of guide sections having identical cross-sections, the product Bicli will exactly equal the product Bzdz at all operating frequencies. Since this condition (Bid1-I-B2d2) in such a .coupler as shown in Fig. 1 .is the required condition for complete cancellation of induced energy in one direction in the auxiliary guide, the 'directivity of such' a coupleris thus seen .to becompletely independent of operating frequency.

Furthermore, in general, reinforcement will occur between the waves which are induced in the auxiliary guide which travel in the direction opposite to the direction in which cancellation occurs. It is only in the very special case where the sum of the phase displacements B1d1 and Bzdz equals some multiple of 21r that cancellation could occur in this direction. Under practical operating conditions, the product B1di or its equal B2012 is generally approximately 1r/2 sqthat their sum is much less than 21r.

- One coupler constructed in this manner using 1 x /2" wave guide with .050" wall thickness was found to have a directivity in excess of 30 decibels when tested over the wavelength range 3.1-3.7 centimeters.- The attenuation of this coupler was measured to be 40 decibels. In this coupler the length of the slots was 0.232 and the width was 0.063. The distance d1 equaled (l2 and its magnitude was 0.517

Fig. 5 shows a modification of the coupler shown in Fig. 3. Main wave guide section II) is again oriented at right angles to auxiliarywave guide section II and has a common broad-wall section therewith. Coupling slots I2 and I3 are cut incthe common wall section parallel to the longitudinal axis of auxiliary wave guide section II and are positioned at equal distances on opposite sides of the center line of auxiliary wave guide II. They are also displaced at equal distances about the center line of mainwave guide I0.

In operation, the slots I2 and I3 serve-to couple the transverse magnetic field of main wave guide I8 to the longitudinal magnetic field of auxiliary wave guide I I. An incident Wave introduced from the left side of main guide III will induce a wave in auxiliary guide I I .in travelling in the direct-ion from coupling slot I2 to coupling slot I3. Cancellation will occur in the opposite direction. .As in the previous example, this cancellation occurs When B1d1=B2dz and the resulting directivity of the coupler is completely independentof frequency when B1=Bz, d1 =dz.

If it is desired to lower the attenuation of the directional couplers shown in Figs. 3 and 5 the area of the slots should be increased. In practice it has been found possible to. increase the slot length to a value which equals one quarter of a wavelength without interfering with the frequency-insensitivity attenuation. Increasing the slot width also lowers the attenuation. If the width is doubled the attenuation decreases approximately 3 decibels. Care must be taken, however, not to make the ratio of length to width too small; otherwise undersirable' electric field coupling occurs with a loss in-directivityr Fig. 6 shows a further modification of the present inventionwhich is a combination of the embodiments shown in Figs. B and 5. As in the previously described couplers, amain wave guide section III is arranged perpendicular to an auxiliarywave guide section II. A pair of crossshaped apertures I2" and I3 are disposedpsymmetrically along a diagonal of the broad Wall face section common to the perpendicular wave guide sections. The distance (1215 measuredralong guide I8 between the eometric centers of apertures I2" and I3, and distance d1 asi'measured along guide I l between the same points. In this modification the coupling slots 12 and I3 of the modification shown in Fig. 3 are, in effect, superimposed upon the coupling slots I2 and I3 of Fig. 5. This results in the pair of cross-shaped apertures I2 and I3". By using the crossshaped apertures, the same frequency-insensitive directivity results when B1=B2 and d1=d2, but because of the larger total slot area with equivalent slotdimensions, this type of coupler has a lower attenuation. In practice, such couplers having slots in the shape of crosses have an attenuation approximately 3 decibels less than the coupler using simple slots having comparable I dimensions.

Another modification of the present invention is shownin Fig. 7. As in the other medications, main wave guide I is oriented at right angles to auxiliary wave guide I l and has a common broad wall section therewith. Coupling slots 20 and 2| are symmetrically located along a diagonal of the common wall section, with slot 20 being parallel to the diagonal and slot 2| being normal to the diagonal. The distances di and 012 for such diagonal slots are measured from the geometric centers and are preferably equal, as are 131 and B2, to" obtain the frequency-insensitivity characteristic of the invention.

One advantage of such a slot arrangement over those shown in Figs. 3 and 5 is that, for a common wall section of a given size, it is possible to have longer slots. This reduces the attenuation as compared with the simple parallel slot arrangement of Fig. 3 or 5, without appreciably affecting the frequency insensitivity of the directivity.

A coupler using 1'' x 1 /2" rectangular guide with .050 wall thickness was built having such diagonal slots whose length was .387 and whose width was .063". The distance d1 was made equal to (Z2 and was .523. When tested over the wavelength range 3.1-3.7 centimeters this coupler was found to have an attenuation of 30 decibels, which is approximately decibels lower than the parallel slot type coupler. The frequency-insensitive directivity remained in the order of 30 decibels over the entire hand.

If still lower attenuation in a directional coupler is desired without lowering the directivity, the modification shown in Fig. 8 is useful. This modification shows wave guide sections I0 and H oriented at right angles and having a common broad-wall section. Crossed slots and 2 I are arranged symmetrically along a diagonal of the common wall section with the arms oriented at 45 to the axes of the wave guide sections forming the coupler. The distances di and d2 are measured along the axes of guides II and I0 respectively from the geometric centers of apertures 20 and 2|. The same frequency-insensitive directivity results with such a coupler as in the simple diagonal slot arrangement of Fig. '7 provided B1=B2 and di dz, but because of the larger total slot area with equivalent slot dimensions, this type of coupler has a lower attenuation. In practice, a coupler having crossed diagonal slots arranged symmetrically along a diagonal of the common wall has an attenuation of approximately 3 decibels less than a coupler using simple diagonal slots having comparable dimensions.

Other forms of wave guide may be used rather than rectangular. If it is desired to use elliptical or circular wave guides instead of rectangular wave guides in the construction of a directional 8 coupler, it is possible to provide a flattened portion in the common wall section where the main and auxiliary units are joined at right angles. By using any of the coupling modifications described above, it will then be possible to construct a directional coupler which has a high directivity which is independent of operating frequency. The mechanical advantage of having the couplers oriented at right angles will also be realized.

In some cases it may be desired to construct a coupler in which the two wave guide sections are not oriented exactly at to each other. Small deviations from the perpendicular arrangement do not change the operation of the coupler, and may easily be made. The only requirement that must be met is that the pair of apertures continue to maintain their diagonally opposite quadrantal positioning on opposite sides of the center line of each wave guide section. This requirement can easily be met even though the angle between the two guides is somewhat less than 90. Of course (21 and 112, each measured along the axis of a respective guide, must maintain the relationship indicated above.

Although the wave guide coupler above discussed was described as using apertures for coupling between the two guides, the present invention is not limited to this particular type of coupling means. Conducting loops or other types of coupling may also be used to link the magnetic fields of the two guides. As illustrated in Figs. 9 and 10, it is possible by the use of a pair of coupling loops 22, 2! in each wave guide section to construct a directional coupler in which the main wave guide section It is separated from the auxiliary wave guide section II. In such a coupler the coupling loops 22, 21 may be connected by a pair of coaxial line sections 25 which have the same electrical length and thus do not disturb the required phase difierence between two induced waves in the auxiliary wave guide.

In order for a coupler having a pair of coupling means, such as apertures or coupling loops, to exhibit high directivity properties, it is necessary that the waves induced in the auxiliary guide section by each of the coupling means must cancel in one direction. That is the two induced waves travelling in one direction must be 180 out of phase. If the directivity is to be independent of frequency the 180 phase diflference must be accomplished in a manner independent of physical dimensions, and thus must be achieved electrically. In transmission lines having a single conductor such as hollow pipe guides, the electrical phase reversal may be achieved, as has been pointed out, by utilizing the magnetic field phase reversal as the wave guide center line is crossed. This phase reversal efiect is in no way dependent upon frequency.

It should be understood, of course, that the functions of the main guide and auxiliary guide in the above couplers may be reversed without in any way changing the operation of the coupler. Because of reciprocity, the same directivity and attenuation will be realized.

One use of such directional couplers is to accurately measure the power being transmitted from an ultra-high-frequency energy source to a suitable load, the accuracy of such measurement being independent of changes in operating frequency and of the presence of standing waves in the transmission line system. The directional coupler is connected with its main guide or line section in tandem with the transmissionv line connecting the source of ultra-high-frequency to 9,, the load A predetermined fraction .of the power travelling inv themain transmission line section is induced into the auxiliary transmission line section. This: fraction is, of course, dependent upon: the attenuation factor ofthe directional coupler selected, and is independent; of; the operat-' ing frequency in. an ideal directional coupler.

A power responsiveelement of. any conven-' tional type,.. such; as a bolometer. or. thermistor, is: located in that end ofthe auxiliary line section toward which the wave inducedtherein, by power travelling. from the source to the;load in the main line section is directed;- By measuring the amount of power of theinduced wave in the auxiliary line and knowing the attenuation of the coupler, it is thus possible to determine the amount of power" travelling in the main line from the sourceto-the load. 'If the directivity of the coupler is high, as it is in a coupler constructed in-accjord'ance with, this invention, little or no energy is induced in the auxiliary line section in the direction away from the power measuring element by the power, travellingflfrom the source to the load. If anysuch residual lowintensity propagation exists in that direction, it may be madeinefiective by terminating that end of the auxiliary line section by a powerabsorbing matched termination of any known typ Power which flows inthe opposite direction in the main line section, suchas' results from refiections occurring at the load, will also tend to induce a wave inthe auxiliary line sectiornbut in a direction away fromvthe power responsive element. The undesirable induced power travelling in the direction away from the power responsive element will be absorbed by the power ab;

sorbing matched termination andv will thus not affect the power responsive element.

Therefore, in such; a; power measuring sys tem, by the use of a directional coupler of this type, the power flowing in one direction in a transmission line may be accurately measured over a wide range of operating frequencies. Furthermore, this measurement is independent of any power flowing in the opposite direction in the transmission line, as may occur when undesired energy reflections exist in the line.

Thus, by the use of the teachings of the present invention, it is possible to construct a directional coupler having a high degree of directivity which is independent of operating frequency. Furthermore, a wave guide coupler constructed in accordance with this invention may have its main and auxiliary wave guides oriented at right angles to each other with their broad faces in contact. It is possible to choose among a wide range of attenuations by suitable design, without decreasing the desired frequency insensitive directivity.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. Ultra high frequency apparatus comprising a first section of rectangular wave guide and a second section of rectangular wave guide oriented substantially at right angles to said first section of wave guide and having a common broad wall section therewith, said first and second wave guide ections beingadapted to convey ultra high frequency electromagnetic energy, said common broad wall section having spaced first and second energy-intercoupling. aperture therein situated,

in diagonally opposite quadrants of said common: broad wallsection as defined by the center lines,

of said wave guides.

2. Ultra high frequency apparatus as defined in.

intercoupling apertures are elongated narrow slits both parallel to the centerline'of onelof said sections of wave ,guide;

. 4. Ultra. high; frequency apparatus as defined in claim 1,;wherein each of, said first and second.

aperturesis. cross-shaped.v

5. Ultra high frequency apparatus as defined in claim 1,.wi1erein each of said first and second apertures: is shapedas two intersecting narrow.

slits, one substantially parallel to the center line of said first section of wave guide and the other.

substantially parallel to the center line of said second section of wave guide.

6. Ultra high frequency apparatus comprising a first section of-rectangular wave guide and a; second section of rectangular wave guide oriented; substantially at right angles to said first section ofwave guide, said first andsecond sections of,

wave guide being each adapted toconvey-ultra high frequency electromagnetic energy, said first and second sections of wave guide each having a substantially squareinternal portion of a broad wall; thereof parallel to and coextensive. with a: second substantially square internal portion,0f broad wall directly opposite in the other of the wave guide sections, said firstand 'secondsquare wall portions defining two pairs of substantially parallel diagonals, and first and second means intercoupling the interior of said first section of wave guide with the interior of said second section of wave guide, said second intercoupling means being symmetrically displaced from said first intercoupling means about a plane containin one pair of parallel diagonals of said first square wall portion and said second square wall portion, said first and second intercoupling means being situated in diagonally opposite quadrants of said parallel substantially square coextensive broad wall portions, the quadrants being defined by the center lines of said wave guides.

7. Ultra high frequency apparatus as defined in claim 6, wherein said first section of wave guide is spaced an appreciable distance from said second section of wave guide, each of said first and second means intercoupling the interior of said first section of wave guide with the interior of said second section of wave guide comprising a coaxial transmission line extending substantially perpendicularly between said first and second substantially square internal wall portions, and having a coupling loop on one end thereof inside said first section of wave guide and a coupling loop on the opposite end thereof inside the second section of wave guide.

8. Ultra-high-frequency apparatus comprising a first section of rectangular wave guide, a second section of rectangular wave guide oriented substantially at right angles to said first section and having a common broad wall section therewith, said first and second Wave guide sections being adapted to convey ultra-high-frequency electromagnetic energy, said common broad wall section having a pair of cross-shaped apertures therein situated in diagonally opposite quadrants.

of said common broad wall section as defined by the center lines of said wave guides, one arm of each of said cross-shaped apertures being oriented parallel to a diagonal of said common broad wall section and the other arm of each of said cross-shaped apertures being oriented normal to said diagonal.

9. Ultra-high-frequency apparatus comprising a first section of rectangular wave guide, a similar second section of rectangular wave guide oriented at substantially right angles to said first section and having a common broad wall section therewith, said first and second wave guide sections being adapted to convey ultra-highfrequency electromagnetic energy, said common broad wall section having a pairof cross-shaped apertures therein situated in diagonally opposite quadrants of said common broad wall section as defined by the center lines of said wave guides, the distances of the geometric centers of said apertures from each of said center lines being equal, and the arms of said cross-shaped apertures being oriented at 45 to said wave guides.

10. Ultra-high-frequency apparatus comprisin a first section of rectangular wave guide, a second section of rectangular wave guide oriented substantially at right angles to said first section of wave guide and having a common broad wall section therewith, said first and second wave guide sections being adapted to convey ultrahigh-frequency electromagnetic energy, said common broad wall section having first and second-energy-intercoupling apertures therein situated in diagonally opposite quadrants of said common broad wall section as defined by the center lines of said wave guides, said apertures being cross shaped.

THEODORE MORENO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED S ATES PAT NTS Number Name 7 7 Date 2,241,119 I Dallenbach May 6,1941 2,416,567. McArthur Feb. 25, 1947 2,423,390 Korman' July 1, 1947, 2,473,274 Bradley June 14, 1949 2,512,191 Wolf June 20, -1950 FOREIGN PATENTS Number Country Date 545,936 Great Britain June 18, 1942 OTHER REFERENCES The Journal of the Institution of Electrical Engineers, vol. 93, Part IIIA (Radiolocation), No. 4, 1946. Radio Section Paper, "Directive Couplers in Wave Guides." by M. Surdin, pp. 725-736'of the magazine. Using page 730 in particular published January 17, 1947, by The Institution, Savoy Place, Victoria Embankment, London W. C; 2. Copy in 178-4411". 

